Article having variable composition coating

ABSTRACT

A coated article includes a substrate and an MCrAlY coating supported on the substrate. The M includes at least one of nickel, cobalt, and iron, Cr is chromium, Al is aluminum, and Y is yttrium. The composition of the MCrAlY coating varies in an amount of at least one of Cr, Al, and Y by location on the substrate with respect to localized property requirements. In one example, the coated article is an article of a gas turbine engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/036,938 filed May 16, 2016, which is a 35 USC 371 national stagefiling of PCT Application Serial No. PCT/US2014/065863, filed Nov. 17,2014, which claims priority to U.S. Provisional Patent Application Ser.No. 61/905,937 filed Nov. 19, 2013, the disclosures of which areincorporated by reference in their entirety herein.

BACKGROUND

A gas turbine engine typically includes a fan section, a compressorsection, a combustor section and a turbine section. Air entering thecompressor section is compressed and delivered into the combustionsection where it is mixed with fuel and ignited to generate a high-speedexhaust gas flow. The high-speed exhaust gas flow expands through theturbine section to drive the compressor and the fan section. Thecompressor section typically includes low and high pressure compressors,and the turbine section includes low and high pressure turbines.Airfoils in the engine can be coated with a ceramic thermal barriercoating to protect the airfoils from the high-temperature gas flow.

SUMMARY

A coated article according to an example of the present disclosureincludes a substrate, an MCrAlY coating supported on the substrate,where the M includes at least one of nickel, cobalt, and iron, Cr ischromium, Al is aluminum, and Y is yttrium. The composition of theMCrAlY coating varies in an amount of at least one of Cr, Al, and Y bylocation on the substrate and with respect to localized propertyrequirements.

In a further embodiment of any of the foregoing embodiments, thelocalized property requirements are selected from the group consistingof corrosion resistance, erosion resistance, spallation resistance,fatigue resistance, oxidation resistance, creep resistance, impactresistance, and combinations thereof.

In a further embodiment of any of the foregoing embodiments, thecomposition of the MCrAlY coating varies in the amount of Cr.

In a further embodiment of any of the foregoing embodiments, thecomposition of the MCrAlY coating varies in the amount of Al.

In a further embodiment of any of the foregoing embodiments, thecomposition of the MCrAlY coating varies in the amount of Y.

In a further embodiment of any of the foregoing embodiments, the MCrAlYcoating includes at least one alloying element of Co, tantalum (Ta),tungsten (W), molybdenum (Mo), silicon (Si), hafnium (Hf), and zirconium(Zr), and the amount of the alloying element differs by location on thesubstrate and with respect to localized property requirements.

In a further embodiment of any of the foregoing embodiments, the MCrAlYcoating includes at least one alloying element of tantalum (Ta),tungsten (W), molybdenum (Mo), and zirconium (Zr), and the amount of thealloying element differs by location on the substrate and with respectto localized property requirements such that the MCrAlY includes atleast one of Ta, W, Mo, and Zr at a first location on the substrate andthe MCrAlY coating is free of any Ta, W, Mo, and Zr at a second locationon the substrate.

In a further embodiment of any of the foregoing embodiments, thesubstrate is an airfoil, and the composition of the MCrAlY coatingvaries between a leading edge of the airfoil and another location on theairfoil to provide better erosion resistance at the leading edgerelative to the other location on the airfoil.

In a further embodiment of any of the foregoing embodiments, the MCrAlYcoating is functionally graded between locations that vary incomposition.

In a further embodiment of any of the foregoing embodiments, the MCrAlYcoating is a continuous coating.

A gas turbine engine according to an example of the present disclosureincludes an article having a substrate and an MCrAlY coating supportedon the substrate, where the M includes at least one of nickel, cobalt,and iron, Cr is chromium, Al is aluminum, and Y is yttrium. Thecomposition of the MCrAlY coating varies in at least one of Cr, Al, andY by location on the substrate with respect to localized propertyrequirements.

The gas turbine engine as recited in claim 11, including a compressorsection, a combustor in fluid communication with the compressor section,and a turbine section in fluid communication with the combustor.

In a further embodiment of any of the foregoing embodiments, thelocalized property requirements are selected from the group consistingof corrosion resistance, erosion resistance, spallation resistance,fatigue resistance, oxidation resistance, creep resistance, impactresistance, and combinations thereof.

In a further embodiment of any of the foregoing embodiments, thecomposition of the MCrAlY coating varies in the amount of Cr.

In a further embodiment of any of the foregoing embodiments, thecomposition of the MCrAlY coating varies in the amount of Al.

In a further embodiment of any of the foregoing embodiments, thecomposition of the MCrAlY coating varies in the amount of Y.

In a further embodiment of any of the foregoing embodiments, the MCrAlYcoating includes at least one alloying element of Co, tantalum (Ta),tungsten (W), molybdenum (Mo), silicon (Si), hafnium (Hf), and zirconium(Zr), and the amount of the alloying element differs by location on thesubstrate and with respect to localized property requirements.

In a further embodiment of any of the foregoing embodiments, the MCrAlYcoating includes at least one alloying element of tantalum (Ta),tungsten (W), molybdenum (Mo), and zirconium (Zr), and the amount of thealloying element differs by location on the substrate and with respectto localized property requirements such that the MCrAlY includes atleast one of Ta, W, Mo, and Zr at a first location on the substrate andthe MCrAlY coating is free of any Ta, W, Mo, and Zr at a second locationon the substrate.

In a further embodiment of any of the foregoing embodiments, thesubstrate is an airfoil in a turbine section of the engine, and thecomposition of the MCrAlY coating varies between a leading edge of theairfoil and another location on the airfoil to provide better erosionresistance at the leading edge relative to the other location on theairfoil.

In a further embodiment of any of the foregoing embodiments, the MCrAlYcoating is functionally graded between locations that vary incomposition.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the present disclosure willbecome apparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

FIG. 1 illustrates a gas turbine engine.

FIG. 2 illustrates a representative portion of a coated article that canbe used in the gas turbine engine of FIG. 1 .

FIG. 3 illustrates a coated airfoil that can be used in the gas turbineengine of FIG. 1 .

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flow path B in abypass duct defined within a nacelle 15, while the compressor section 24drives air along a core flow path C for compression and communicationinto the combustor section 26 then expansion through the turbine section28. Although depicted as a two-spool turbofan gas turbine engine in thedisclosed non-limiting embodiment, it should be understood that theconcepts described herein are not limited to use with two-spoolturbofans as the teachings may be applied to other types of turbineengines including three-spool architectures.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a first (or low) pressure compressor 44 and afirst (or low) pressure turbine 46. The inner shaft 40 is connected tothe fan 42 through a speed change mechanism, which in exemplary gasturbine engine 20 is illustrated as a geared architecture 48 to drivethe fan 42 at a lower speed than the low speed spool 30. The high speedspool 32 includes an outer shaft 50 that interconnects a second (orhigh) pressure compressor 52 and a second (or high) pressure turbine 54.A combustor 56 is arranged in exemplary gas turbine 20 between the highpressure compressor 52 and the high pressure turbine 54. A mid-turbineframe 57 of the engine static structure 36 is arranged generally betweenthe high pressure turbine 54 and the low pressure turbine 46. Themid-turbine frame 57 further supports bearing systems 38 in the turbinesection 28. The inner shaft 40 and the outer shaft 50 are concentric androtate via bearing systems 38 about the engine central longitudinal axisA which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path C. The turbines 46, 54 rotationally drivethe respective low speed spool 30 and high speed spool 32 in response tothe expansion. It will be appreciated that each of the positions of thefan section 22, compressor section 24, combustor section 26, turbinesection 28, and fan drive gear system 48 may be varied. For example,gear system 48 may be located aft of combustor section 26 or even aft ofturbine section 28, and fan section 22 may be positioned forward or aftof the location of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegeared architecture 48 is an epicyclic gear train, such as a planetarygear system or other gear system, with a gear reduction ratio of greaterthan about 2.3 and the low pressure turbine 46 has a pressure ratio thatis greater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five 5:1. Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The geared architecture 48 may be an epicycle geartrain, such as a planetary gear system or other gear system, with a gearreduction ratio of greater than about 2.3:1. It should be understood,however, that the above parameters are only exemplary of one embodimentof a geared architecture engine and that the present invention isapplicable to other gas turbine engines including direct driveturbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, withthe engine at its best fuel consumption—also known as “bucket cruiseThrust Specific Fuel Consumption (‘TSFC’)”—is the industry standardparameter of lbm of fuel being burned divided by lbf of thrust theengine produces at that minimum point. “Low fan pressure ratio” is thepressure ratio across the fan blade alone, without a Fan Exit Guide Vane(“FEGV”) system. The low fan pressure ratio as disclosed hereinaccording to one non-limiting embodiment is less than about 1.45. “Lowcorrected fan tip speed” is the actual fan tip speed in ft/sec dividedby an industry standard temperature correction of [(Tram ° R)/(518.7°R)]^(0.5). The “Low corrected fan tip speed” as disclosed hereinaccording to one non-limiting embodiment is less than about 1150ft/second.

FIG. 2 illustrates a representative portion of a coated article 60 thatcan be used in the gas turbine engine 20. For example, the article 60can be an airfoil, such as a blade or vane, a blade outer air seal, arotor disk, or other article that would benefit from the examplesdisclosed herein. The article 60 includes a substrate 62 and an MCrAlYcoating 64, which can also include MCrAlYX, where X is additionalalloying elements, supported on the substrate 62. The M is a metal andincludes at least one of nickel (Ni), cobalt (Co), and iron (Fe), Cr ischromium, Al is aluminum, and Y is yttrium. In one example, the MCrAlYcoating 64 is a continuous coating on the substrate 62.

The substrate 62 can be a structural body of the article or anintermediate coating that is between the MCrAlY coating 64 and astructural body of the article, for example. Example substrates can benickel-based alloys, iron-nickel-based alloys, cobalt-based alloys,molybdenum-based alloys and niobium-based alloys, but are not limited tothese.

The composition of the MCrAlY coating 64 varies in an amount of at leastone of the Cr, Al, and Y by location on the substrate 62 with respect tolocalized property requirements. For example, as shown in FIG. 2 , theMCrAlY coating 64 has a first composition at a first location L1 and asecond, different composition at a second location L2 with respect tothe amount of at least one of the Cr, Al, and Y. In further examples,the amounts of additional alloy elements can also vary with respect tolocalized property requirements. The additional alloy elements caninclude Co, tantalum (Ta), tungsten (W), molybdenum (Mo), silicon (Si),hafnium (Hf), zirconium (Zr), and combinations thereof.

The composition of the MCrAlY coating 64 varies by location to tailorthe properties of the MCrAlY coating 64 with respect to localizedproperty requirements. For example, the article 60 can have differentrequirements for oxidation, corrosion, erosion, spallation resistance,creep, fatigue, impact resistance, or combinations thereof that dependon location on the article 60. By varying the composition betweendifferent locations on the article 60, the localized propertyrequirements can be tailored to the particular locations and thus canenhance durability of the article 60.

In further examples, varying the amount of Cr influences corrosionresistance and spallation resistance. For instance, greater amounts ofCr can provide higher resistance to corrosion and spallation. The Cr canalso increase hot corrosion resistance, improve oxidation resistance andreduces Al requirement for formation of an alumina scale. An excessamount of Cr can lower creep strength.

Varying the amount of Al can influence bonding with an optionalceramic-based thermal barrier overcoat, represented at 66. For instance,the Al oxidizes and forms an alumina scale that facilitates strongbonding with the overcoat 66. Greater amounts of Al can provide a morerobust scale for better bonding with the overcoat 66 and alsoimprovement of oxidation resistance.

Varying the amount of Y influences oxidation and corrosion resistance.For instance, greater amounts of Y can provide higher resistance tooxidation and corrosion. Thus, by varying the amounts of at least one ofCr, Al, and Y, the properties of the MCrAlY coating 64 can be tailoredwith respect to localized property requirements.

Varying the amount of Ta, Mo and W reduces diffusivity of aluminum tothe surface of the coating 64, which slows oxide growth rate andenhances oxidation resistance. The Ta can also be used to increasestrength, increase oxidation strength and improve resistance to hotcorrosion.

The Ta, Mo and W can also be added to provide a closer compositionalmatch to an underlying alloy of the substrate 62. In one example, theunderlying alloy of the substrate 62 can have a nominal composition, byweight, of 5% Cr, 10% Co, 5.65% Al, 1.9% Mo, 5.9% W, 8.7% Ta, 0.10% Hf,3.0% Re and remainder Ni. Using a similar composition between substrate62 and the coating 64 facilitates a reduction in interdiffusion of Ta,Mo and W, and thus increases oxidation life.

Relatively higher amounts of Si can increase oxidation resistance andtype II hot corrosion resistance. Using excess Si can reduce the meltingpoint of the coating 64 and potentially also of an underlying substratenickel alloy.

Relatively higher amounts of Hf and Zr can increase adherence of aluminaand chromia scales, and reduce spallation of overlying ceramic thermalbarrier coating layers during thermal cycling. The Hf and Zr may alsocombine with sulfur and prevent sulfur from segregating to the oxidelayer.

Relatively higher amounts of Co can increase microstructural strengthand provide stability (reduces creep).

In a further example, the MCrAlY coating 64 can have a functionallygraded region 68 (laterally graded) between the first location L1 andthe second location L2. The functionally graded region 66 is acompositional transition from the composition of the MCrAlY coating 64in the first location L1 to the composition of the MCrAlY coating 64 inthe second location L2.

The relative differences in the amounts of one or more of the Cr, Al,and Y between locations L1 and L2 can also be varied by a predeterminedcritical amount to provide a targeted difference in one or more givenproperties between the locations L1 and L2. In one example, thecomposition of the MCrAlY coating 64 in locations L1 and L2 with respectto the amount of Cr differs by 4-40 wt %. In a further examples of anyof the examples herein, the composition of the MCrAlY coating 64 inlocations L1 and L2 with respect to the amount of Al differs by up to 8wt % and in some examples by at least 0.2 wt %. In a further examples ofany of the examples herein, the composition of the MCrAlY coating 64 inlocations L1 and L2 with respect to the amount of Y differs by up to 0.8wt % and in some examples by at least 0.2 wt %.

In a further examples of any of the examples herein, the composition ofthe MCrAlY coating 64 in locations L1 and L2 differs with respect to anamount of Ta, W, Mo, Zr, or combinations thereof. In further examples,the composition of the MCrAlY coating 64 in one of the locations L1 orL2 includes Ta, W, Mo, Zr, or combinations thereof and the compositionof the MCrAlY coating 64 in the other of the locations L1 or L2 is freeof any Ta, W, Mo, Zr, or combinations thereof.

In a further examples of any of the examples herein, the composition ofthe MCrAlY coating 64 in locations L1 and L2 with respect to the amountof Co differs by up to 14 wt % and in some examples by at least 1 wt %.

In a further examples of any of the examples herein, the composition ofthe MCrAlY coating 64 in locations L1 and L2 with respect to the amountof Si differs by up to 0.55 wt % and in some examples by at least 0.1 wt%.

In a further examples of any of the examples herein, the composition ofthe MCrAlY coating 64 in locations L1 and L2 with respect to the amountof Hf differs by up to 0.5 wt % and in some examples by at least 0.1 wt%.

The differences in the amounts of the above elements facilitateproviding a tangible property difference between the locations L1 and L2of the MCrAlY coating 64. Table 1 below includes additional exampleCompositions I-IV that can be used in locations L1 and L2, asstand-alone coatings or as bond coats for overcoat 66. It is to beunderstood that the below-example compositions may or may not includeadditional impurity elements.

TABLE 1 Example Compositions I-IV Composition Composition CompositionComposition Elements I II III IV Chromium 5.50-7.00 15.00-19.0011.00-14.00 29.5-45.5 Cobalt 10.00-13.00 20.00-24.00 11.00-14.0015.00-19.00 Aluminum 9.00-11.5 11.80-14.5  7.50-9.50 6.50-9.20 Tantalum3.00-6.00 Tungsten 3.00-6.00 Molybdenum 3 Jan. Yttrium 0.30-0.700.40-0.80 0.20-0.60 0.25-0.75 Hafnium 0.20-0.60 0.10-0.40 0.10-0.500.10-0.40 Silicon 0.10-0.30 0.20-0.60 0.10-0.30 0.15-0.65 Zirconium0.10-0.20 0.10-0.20 Sulfur   0-0.01    0-0.010   0-0.01   0-0.01 OtherElements   0-0.50   0-0.50   0-0.50   0-0.50 Nickel Remainder RemainderRemainder Remainder

FIG. 3 illustrates another example coated article 160. In this example,the coated article 160 is an airfoil that can be used in the gas turbineengine 20. For example, the airfoil 160 can be a turbine airfoil in theturbine section 28 of the engine 20, but is not limited to turbineairfoils. In this example, the airfoil 160 includes the MCrAlY coating64 continuously supported on the outer surface thereof. The airfoil 160has a leading edge LE and a trailing edge TE that are joined by opposedfirst and second sides 70 a/70 b. The leading edge of the airfoil 160can be susceptible to high temperatures and impact from foreign objectsin the gas stream that flows across the surfaces of the airfoil 160.Thus, the MCrAlY coating 64 varies in composition between the leadingedge of the airfoil 160 and the other locations of the airfoil 160,represented at 72, to provide better thermal resistance and erosionresistance at the leading edge relative to the other locations 72 on theairfoil 160. Similarly, the composition of the MCrAlY coating 64 can bevaried to enhance corrosion, spallation resistance, fatigue, or otherproperty of interest by location on the airfoil 160. In another example,the second side 70 b can be susceptible to high temperatures, oxidationor thermal barrier coating spallation, while a platform 74 requiresoxidation resistance and corrosion resistance. The MCrAlY coating 64 canvaries in composition between the second side 70 b of the airfoil 160and the platform 74 to provide the desired properties in each location.

Although a combination of features is shown in the illustrated examples,not all of them need to be combined to realize the benefits of variousembodiments of this disclosure. In other words, a system designedaccording to an embodiment of this disclosure will not necessarilyinclude all of the features shown in any one of the Figures or all ofthe portions schematically shown in the Figures. Moreover, selectedfeatures of one example embodiment may be combined with selectedfeatures of other example embodiments.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this disclosure. The scope of legal protection given tothis disclosure can only be determined by studying the following claims.

What is claimed is:
 1. A coated article comprising: a substrate; and anMCrAlY coating supported on the substrate, where the M includes at leastone of nickel, cobalt, and iron, Cr is chromium, Al is aluminum, and Yis yttrium, the composition of the MCrAlY coating varying in an amountof at least one of Cr, Al, and Y by lateral location on the substrateand with respect to localized property requirements of the coatedarticle, wherein the coating is functionally graded between locationsthat vary in composition.
 2. The coated article as recited in claim 1,wherein the localized property requirements are selected from the groupconsisting of corrosion resistance, erosion resistance, spallationresistance, fatigue resistance, oxidation resistance, creep resistance,impact resistance, and combinations thereof.
 3. The coated article asrecited in claim 1, wherein the composition of the MCrAlY coating variesin the amount of Cr.
 4. The coated article as recited in claim 1,wherein the composition of the MCrAlY coating varies in the amount ofAl.
 5. The coated article as recited in claim 1, wherein the compositionof the MCrAlY coating varies in the amount of Y.
 6. The coated articleas recited in claim 1, wherein the MCrAlY coating includes at least onealloying element of Co, tantalum (Ta), tungsten (W), molybdenum (Mo),silicon (Si), hafnium (Hf), and zirconium (Zr), and the amount of thealloying element differs by location on the substrate and with respectto the localized property requirements.
 7. The coated article as recitedin claim 1, wherein the MCrAlY coating includes at least one alloyingelement of tantalum (Ta), tungsten (W), molybdenum (Mo), and zirconium(Zr), and the amount of the alloying element differs by location on thesubstrate and with respect to the localized property requirements suchthat the MCrAlY includes at least one of Ta, W, Mo, and Zr at a firstlocation on the substrate and the MCrAlY coating is free of any Ta, W,Mo, and Zr at a second location on the substrate.
 8. The coated articleas recited in claim 1, wherein the substrate is an airfoil, and thecomposition of the MCrAlY coating varies between a leading edge of theairfoil and another location on the airfoil to provide better erosionresistance at the leading edge relative to the other location on theairfoil.
 9. The coated article as recited in claim 1, wherein the MCrAlYcoating is a continuous coating.
 10. A gas turbine engine comprising: anarticle having a substrate and an MCrAlY coating supported on thesubstrate, where the M includes at least one of nickel, cobalt, andiron, Cr is chromium, Al is aluminum, and Y is yttrium, the compositionof the MCrAlY coating varying in at least one of Cr, Al, and Y bylateral location on the substrate with respect to localized propertyrequirements of the coated article, wherein the coating is functionallygraded between locations that vary in composition.
 11. The gas turbineengine as recited in claim 10, including a compressor section, acombustor in fluid communication with the compressor section, and aturbine section in fluid communication with the combustor.
 12. The gasturbine engine as recited in claim 10, wherein the localized propertyrequirements are selected from the group consisting of corrosionresistance, erosion resistance, spallation resistance, fatigueresistance, oxidation resistance, creep resistance, impact resistance,and combinations thereof.
 13. The gas turbine engine as recited in claim10, wherein the composition of the MCrAlY coating varies in the amountof Cr.
 14. The gas turbine engine as recited in claim 10, wherein thecomposition of the MCrAlY coating varies in the amount of Al.
 15. Thegas turbine engine as recited in claim 10, wherein the composition ofthe MCrAlY coating varies in the amount of Y.
 16. The gas turbine engineas recited in claim 10, wherein the MCrAlY coating includes at least onealloying element of Co, tantalum (Ta), tungsten (W), molybdenum (Mo),silicon (Si), hafnium (Hf), and zirconium (Zr), and the amount of thealloying element differs by location on the substrate and with respectto the localized property requirements.
 17. The gas turbine engine asrecited in claim 10, wherein the MCrAlY coating includes at least onealloying element of tantalum (Ta), tungsten (W), molybdenum (Mo), andzirconium (Zr), and the amount of the alloying element differs bylocation on the substrate and with respect to the localized propertyrequirements such that the MCrAlY includes at least one of Ta, W, Mo,and Zr at a first location on the substrate and the MCrAlY coating isfree of any Ta, W, Mo, and Zr at a second location on the substrate. 18.The gas turbine engine as recited in claim 10, wherein the substrate isan airfoil in a turbine section of the engine, and the composition ofthe MCrAlY coating varies between a leading edge of the airfoil andanother location on the airfoil to provide better erosion resistance atthe leading edge relative to the other location on the airfoil.